Tuesday, December 9, 2014

Stena Line, one of the largest ferry operators in the world, recently announced that it will convert its 1500 passenger ferry, the Stena Germanica, to methanol propulsion by the year 2015.

In co-operation with Methanex and engine manufacture, Warrtsila, the Stena Germanica will be converted into a methanol powered sea vessel at the Remontova Shipyard in Poland starting in January of 2015. Converting the Stena Germanica to run on methanol fuel is estimated to take six weeks at a cost of $28 million.

The ferry will run the same route as it currently does, between Gothenburg, Sweden and Kiel, Germany. The Stena Line company argues that the use of methanol will reduce the ship's sulphur emissions by 99% and it's nitric oxide emissions by 60%.

Methanol can, of course, be derived from carbon neutral energy sources such as biomass and the synthesis of renewable hydrogen from water with renewable CO2 extracted from the atmosphere or seawater. Enabling ships to be fueled with carbon neutral methanol could eventually eliminate the contribution of greenhouse gasses from large ocean going vessels into the Earth's atmosphere.

Tuesday, September 30, 2014

Establishing a permanent human presence beyond our planet of evolutionary origin is one of the long term goals of human space travel. The expansion of human settlements throughout the solar system has the potential to dramatically increase the economic wealth of human civilization while also greatly enhancing the survival of our species.

Some space advocates believe that the long term colonization of the solar system will require the manufacture of titanic artificial worlds that rotate to produce simulated Earth-like gravities within their interior surfaces. But there are still others who believe that low gravity worlds such as the Moon and Mars could be utilized as near term destinations for human colonization.

But can Homo sapiens really live and reproduce on hypogravity worlds?

In his classic 1972 song 'Rocket Man', Elton John says: "Mars ain't the kind of place to raise the kids..."

Well, maybe!

Planets and Moons within the solar system that are potentially suitable for human colonization:

Moon

surface gravity relative to the Earth: 0.17g

diameter relative to the Earth: 27.3%

surface area relative to the Earth: 7.4%

Mars

surface gravity relative to the Earth: 0.38g

diameter relative to the Earth: 53.1%

surface area relative to the Earth: 28.4%

Mercury

surface gravity relative to the Earth: 0.38g

diameter relative to the Earth: 38.3%

surface area relative to the Earth: 14.7%

Callisto

surface gravity relative to the Earth: 0.13g

diameter relative to the Earth: 37.8%

surface area relative to the Earth: 14.3%

Note: Land area comprises ~ 29% of the Earth's surface with ~71% covered by water

Continuous exposure to microgravity conditions over weeks and months
is inherently deleterious to human health. And there is growing evidence
that long term microgravity exposure can also significantly lower
fertility in humans and other mammals, possibly leading to sterility.
This suggest that crewed interplanetary missions requiring several
months of space travel may require interplanetary vehicles capable of
producing artificial gravity during the journey. Obviously, humans can't
colonize Mars by sterilizing their passengers before they get there!

But it is currently unknown how much gravity is required to mitigate or eliminate significant infertility in humans. However, if the lower gravity of the Moon or Mars turns out to seriously effect the long term fertility of humans then daily exposure to-- hypergravity-- through short armed centrifuges may be a possible solution.

Short radius hypergravity centrifuge could help to mitigate the possibility of infertility on lower gravity worlds such as the Moon and Mars.
(Credit NASA)

But the lower gravity on extraterrestrial worlds could have another deleterious
effect that may effect human reproduction and even the ability of people to
return to the normal gravity of the Earth's surface. Bone mineral loss under microgravity conditions is already known to occur in astronauts living in space for several weeks. And significant bone loss could distort the shape of the female pelvis to a degree that endangers her and a potential infant during attempted childbirth. Unfortunately, while hypergravity centrifuges may mitigate muscle loss in low gravity environments, they appear to have no effect on bone mineral loss. Rigorous exercise in microgravity, however, does seem to lower the rate of bone mineral loss-- but does not stop it.

Predicted time limits beyond the Earth for significant bone loss in humans that could risk skeletal fractures once astronauts return to Earth

Space (microgravity) - 36 weeks (60 weeks with exercise)

Moon (1/6 gravity) - 96 weeks

Mars (2/5 gravity) - 159 weeks

The predicted level of tolerable bone loss for humans in space is about
36 weeks. However, if astronauts exercise rigorously for a few hours
every day then their stay in space can be extended to 60 weeks (more
than a year). So it seems logical that rigorous exercise should enable
humans to mitigate or even eliminate significant bone mineral loss under the
hypogravity conditions of the Moon and Mars.

Having some gravity could make it possible for people to
use heavily weighted vest or backpacks in order to avoid bone mineral loss while
maintaining their Earthling strength-- even without daily strenuous exercise. While lifting weights can strengthen the arms, weighted vest or backpacks producing an Earth-like weight to be carried by their hindlimbs would strengthen the legs which are normally physiologically weakened under microgravity and low gravity environments.,Within pressurized habitats on the Moon an Mars, heavily weighted vest could be worn throughout the day, providing exercise for the leg muscles when standing, walking, running and jumping.

However, children and infants who are born on the Moon and Mars may also have to wear weighted vest on a regular basis soon after they are born if their bodies are to grow and develop properly on such low gravity worlds. But it would appear that humans should be able to live and reproduce on low gravity planets and moons such as the Moon and Mars if they wear the appropriate clothing (weight vest or weight packs) while periodically experiencing hypergravity on a short armed centrifuge.

Of course, Homo sapiens is a species that it use to modifying its clothing and its habitats in order to survive in more hostile environmental. That's why human ancestors were able to radiate from the tropical regions of Africa into the wintery weather of Europe, Northern Asia, and eventually North America-- especially during the Earth's glacial periods.

Thursday, September 18, 2014

Humanity currently exist in a global energy economy that is dominated by fossil fuels. And the combustion of fossil fuels by our industrial civilization has created atmospheric conditions with an ever increasing CO2 (carbon dioxide) content. The carbon dioxide in the Earth's atmosphere is now higher than it has ever been in the history of the human species. In fact, it is higher than in the entire history of our genus, Homo, which first emerged in sub-Saharan Africa more than 2.5 million years ago.

At approximately 400 parts per million, current CO2 levels in the Earth's atmosphere may be as high as they were during the Pliocene Epoch when sea levels may have been 10 to 40 meters higher than they are today. And as long as we continue to use fossil fuels, the CO2 content in the Earth's atmosphere is likely to reach levels not seen since the Earth was devoid of polar ice caps altogether which could eventually raise global sea levels above 60 meters.

So thanks to the humongous energy needs of our modern civilization, future generations face the possibility of living in a much warmer world with substantially higher sea
levels. Rising sea levels could eventually flood most of the world's coastal areas including some of the world's major cities.

Altruistically, our current civilization should be trying to create a better tomorrow for future generations. Unfortunately, there are global economic interest that have tens of trillions of dollars invested in the fossil fuel economy. And their priorities are to make near term profits-- even at the expense of humanity's long term environmental and economic future. Of course, America's capitalist system exist within a government of the people, by the people, and for the people. So within a democratic republic, free people have the ultimate responsibility to make sure that our civilization doesn't wreck the environment for future generations.

While there are viable technological alternatives to the fossil fuel economy, there are many who actually fear the-- best technological solution-- to the problem of global warming and the deposition of excess CO2 in the Earth's atmosphere: nuclear energy.

Commercial nuclear power is the principal carbon free producer of electricity in the United States, producing more than three times as much carbon free electricity as hydroelectricity, six times as much as wind, and more than 100 times as much carbon free electricity as solar. And this is in spite the fact that the United States pretty much halted the building of new nuclear power plants in the US for more than thirty years.

Commercial nuclear energy is also the safest form of electricity production ever created. Even if you include the accidents at Chernobyl, Fukushima, and Three Mile Island, nuclear energy production is still substantially safer than using coal, natural gas, hydroelectricity, solar, or wind.

Although the United States has more commercial nuclear reactors in operation than any other nation on Earth, the construction of new reactors in the US still lags well behind China and Russia and even behind India, and Europe. While the next generation of small centrally mass produced nuclear reactors should be
available for commercial service in the US by the 2020's, the future domestic demand for such
reactors by US utilities is still clouded by the fact that there is still no
long term solution to the political problem of spent fuel which is often referred to as nuclear waste.

Number of nuclear reactors currently (9/18/2014) under construction by nation:

What to do with the spent fuel once its removed from commercial nuclear reactors is one of the most difficult political obstacles hampering the approval and construction of new nuclear reactors in the US. Within some American States, it is even illegal to build new nuclear reactors until there is a permanent repository or another long term solution to the problem of nuclear waste.

The irony in all of this, of course, is the fact that relative to other electric power producing facilities, nuclear power plants actually create very little toxic waste. A 1000 MWe nuclear power plant only produces about 27 tonnes of spent fuel every year. That's a quantity that is so small that all of the radioactive material ever produced from the commercial nuclear power industry in the US could be placed in an area the size of a football field only a few meters high. That's it!

A 1000 MWe coal power plant, on the other hand, produces approximately 400,000 tonnes of toxic material every year: ash from coal power plants that is contaminated with toxic materials such as mercury, arsenic, chromium, and cadmium which can contaminate drinking water supplies and damage the human nervous system and other vital organs. The ash pumped into the atmosphere of a coal power plants also expose surrounding populations to approximately 100 times more background radiation than a nuclear power plant does. Coal power plants, of course, are the primary producers of greenhouse gasses amongst electric power facilities.

But even solar energy produces substantially more toxic waste than commercial nuclear reactors. Per kilowatt of electricity produced, the toxic materials required to produce rooftop solar panels and the toxic materials contained in the dismantling of solar panels is quantitatively at least 10,000 times that of the toxic materials produced from the nuclear industry. So the toxic waste produced from commercial nuclear power plants is miniscule compared to the toxic waste produced from the solar panel industry.

Ironically, most of the spent fuel produced from a commercial nuclear power plant is actually not waste at all. More than 95% of the fissile and fertile material contained in spent fuel can actually be recycled. This is already been successfully done to a partial degree in countries like France where plutonium is extracted from spent fuel and then mixed with depleted uranium 238.

But way back in 1982, the Shippingport Atomic Power Station in Beaver County, Pennsylvania was shut down after utilizing enriched uranium in a blanket of thorium 232 for five years. In 1987, it was reported that the core of the light water thorium reactor contained 1.3% more fissile material than it had when it was originally fueled. This clearly demonstrated that a light water breeder reactor could produce more fissile material than it consumed if fissile material was utilized in a blanket of fertile thorium.

So plutonium could be extracted from the spent fuel of Light Water Reactors and mixed with thorium in order to produce carbon free electricity in Light Water Thorium Reactors while burning up the plutonium. The fissile uranium produced from the conversion of thorium 232 into uranium 233 could then be mixed with the with depleted uranium or reprocessed uranium from spent fuel to produce
power in current Light Water Reactors. Burning plutonium from spent
fuel in Light Water Thorium Reactors while utilizing
uranium 233 from thorium reactors for reuse in Light Water Uranium Reactors
could demonstrate that more than 95% of the material in spent fuel can
be recycled. Recycling the fissile material in spent fuel would dramatically reduce
the already meager amount of radioactive material that has to be
sequestered into nuclear waste site. And this could help to end the prohibition against building
new nuclear reactors in some States in the United States.

However, the moderation of neutrons could be reduced if the water content of the thorium reactor were reduced by 25 to 50%. This would allow the reactor to burn the other radioactive waste products in a solid fuel mix with plutonium and thorium. That, of course, would completely eliminate the need to bury any spent fuel products created by commercial nuclear reactors.

There's only enough-- terrestrial uranium-- to produce all of the electricity and synfuels required to power all of human civilization at current levels for about 15 years. However, there's more than 4 billion tonnes of uranium in seawater, enough provide all of the energy needs for human civilization for more than 3600 years. Recycling the spent uranium and might extend this to over 5000 years. Utilizing the plutonium from Uranium Light Water Reactors to power Thorium Light Water Reactors, could power human civilization for 2800 years.

So a uranium and thorium economy could power human civilization at current levels for nearly 8000 years. Beyond this point, plutonium/uranium breeder reactors would finally be required to continue to power human civilization on Earth by solely using nuclear fission.

Thorium deposits on the lunar surface (credit:NASA)

However, additional sources of thorium could be mined on the surface
of the Moon, a resource that's only a few days away by chemical rockets.
Because there is no life on the Moon, thorium could be exploited much
more extensively on the lunar surface than on Earth, perhaps to a level
that could allow lunar thorium to power a nuclear fuel
economy on Earth forever.

Launching human crews from the surface of the Earth to low Earth orbit (LEO) requires a delta-v of more than 9.3 kilometers per second (km/s). But on the Moon and Mars, the delta-v requirements are significantly lower. Launching humans from the surface of the Moon to lunar orbit can require as little delta-v as 1.87 km/s. And launching human crews from the surface of Mars to low Mars orbit requires a delta-v of only 4.4 km/s.

Landing humans on the surface of the Earth and on the Moon is relatively easy. Only minuscule amounts of delta-v are required to for crews to leave Earth orbit and glide or parachute through the Earth's thick atmosphere to the terrestrial surface. The delta-v required to land a crew on the surface of the Moon from lunar orbit is equivalent to the delta-v required to leave the lunar surface to low lunar orbit.

Unfortunately, landing crews and large payloads on the surface of Mars is much more problematical. The largest spacecraft that NASA has managed to safely deploy to the
Martian surface are all below 600 kilograms in mass. The weight of a
lunar derived crewed vehicle to the Martian surface is likely to weigh as much as 10 tonnes, not including the substantial amounts of fuel needed to return
to orbit around the Red Planet. And NASA eventually wants the ability to deploy as much as 100 tonnes of payload onto the martian surface by a single spacecraft.

Notional ballutes designed to aerobrake into a planetary orbit or to land on the surface of Mars (Credit: NASA)

The problem with landing large masses on the surface of Mars is that even though the martian atmosphere is approximately 1% as dense as the Earth's atmosphere, it's still thick enough to produce substantial amounts of frictional heating as a vehicle plunges at hypersonic speeds through its atmosphere but still not enough friction to sufficiently lower the terminal velocity as it approaches the planet's surface. Small vehicles (less than 600 kg) attempting to land on Mars have, therefore, been designed to have a high drag coefficients. Designing a spacecraft with a high drag coefficient for vehicles weighing several tonnes or more, however, is much more difficult.

This has pushed NASA towards the idea of utilizing large inflatable ballutes to assist heavy payloads and spacecraft entering the martian atmosphere. The large drag coefficient of a toroidal ballute could allow a spacecraft to decelerate at very low densities high in the martian atmosphere with relatively low rates of frictional heating. The low frictional heat experienced by the ballute could allow for light-weight construction techniques that could enhance the ability to deploy more mass to the martian surface. Ballutes inflated with gases that are lighter than the carbon dioxide could also increases static lift. Recent studies suggest that a toroidal ballute with a tube radius of 80 meters could be used to deliver masses the martian surface of approximately 100 tonnes.

Top: ETLV-2 vehicle designed for landing on the surfaces of the Moon and the moons of Mars; Bottom: An ETLV-2 derived Ares 2 vehicle designed to dock with a disposable heat shield and compacted ballute in order to land on the surface of Mars.

Placed on the surface of Mars, a single staged reusable vehicle with an inert weight of approximately 10 tonnes (including payload and crew) designed to travel to and from the lunar surface would require at least 18 tonnes of fuel to transport a crew from the martian surface to low Mars orbit; 22 tonnes of fuel would be required to reach the surface of Phobos and 24 tonnes of fuel would be needed to reach the surface of Deimos from the martian surface. So with a delta-v requirement of less than 5.3 km/s, a fueled single staged crew vehicle weighing nearly 40 tonnes placed on the surface of Mars should be capable of traveling all the way from the martian surface to the surface of Deimos or to high Mars orbit.

Left: Ares 2 docked with a compacted (pre-deployed) ballute, configured to inject the spacecraft towards an aerobraking encounter with the martian atmosphere. Right: After the rocket burn towards Mars, the Ares 2 would reconfigure itself in order to protect the spacecraft and to inflate the ballute in order to aerobrake and to descend through the martian atmosphere.

A liquid hydrogen and oxygen producing water and fuel depot derived from a reusable orbital transfer vehicle. The Ares 2 landing vehicle would fuel up up at the orbital depot before docking with the compacted ballute/heat shield unit. Water would be transferred to the fuel depot from water factories on the martian moons, Deimos and Phobos.

Water factory would utilize mobile microwave water bugs to extract water from the regolith of the martian moons, Deimos and Phobos; WFD-LV would convert water into fuel to launch water to fuel manufacturing depot in high Mars orbit.

A ballute capable of deploying nearly 40 tonnes to the martian surface
could also easily deploy habitats and cargo larger than those
contemplated for the Altair vehicle to the lunar surface. Cargo missions to the martian surface could utilize ballutes to deploy
mobile robots for excavating and sintering the surface of Mars to
create landing and launch pads for crewed shuttle vehicles and for
regolith shielded outpost similar to those that could be utilized on the
lunar surface.

Hydrogen inflated ballute would enable the crewed Ares 2 vehicle to aerobrake and land on the martian surface.

Small nuclear reactors would also need to be deployed
to power the martian outpost at night or during periods when sandstorms
block out significant amounts of sunlight. Methanol/oxygen fuel cell
electric power plants could also be deployed as back up power, utilizing methanol
produced from the pyrolysis of human biowaste and oxygen extracted from
atmospheric carbon dioxide or from the electrolysis of water.

Water
factories than mine water from the martian regolith would also need to be deployed. Mobile microwave robots
could be used to melt the ice contained in the martian regolith. Water, of course, is essential for drinking, washing, and growing food but is also essential for the production of oxygen for air. Hydrogen and oxygen can also be used to produce hydrogen and oxygen to fuel the reusable shuttle craft.

Ares 2 hovers near the sintered landing area of a martian outpost.

Under the scenario presented here, fuel depots and rotational human
outpost would already be placed in high Mars orbit a few years before the first crewed missions to the martian surface along with water and fuel
producing facilities on the surface of the martian moons, Deimos and
Phobos. Human interplanetary missions to Mars orbit would utilize an
orbital transfer vehicle operating between the Earth-Moon Lagrange
points and high Mars orbit.

Such an interplanetary orbital transfer
vehicle would utilize fuel manufactured from water exported from the lunar poles when going to high Mars orbit and fuel manufactured from water from
the martian moons when returning to cis-lunar space. Such crewed
missions would already transport reusable Ares ETLV-2 vehicles to Mars
orbit for docking with orbiting space habitats or transferring crews to
the surface of the moons of Mars. A single SLS launch could deploy one
or two compacted ballutes plus heat shields to high Mars orbit for one
or two human missions to the martian surface.

Three solar powered regolith shielded habitat modules joined together by two inflated corridors. Additional power for the outpost would be provided by a couple of small nuclear reactors buried beneath the regolith, a few hundred meters away.

The Ares ETLV-2 (Ares 2) would fuel up in high Mars orbit at a OTV
derived fuel depot before docking with a ballute/heat shield unit. The
Ares ETLV- 2 would thin boost the Mars landing vehicle towards Mars.
During the short journey from high Mars orbit towards Mars, the Ares 2
would reconfigure itself while also deploying the ballute. The ballute
would allow the Ares 2 to aerobrake into orbit around Mars and then
descend into the martian atmosphere. The final vertical descent to the
martian surface would first drop off the protective heat shield,
allowing Ares 2 rockets to slow down the final descent to the sintered
surface of a martian outpost.

Ares 2 (Ares ETLV-2) about to be fueled for take-off by a mobile LH2/LOX cryotanker.

Tuesday, June 24, 2014

Twin Regolith shielded habitats on a sintered lunar surface area. Each habitat module is connected to each other by an inflatable pressurized walkway.

Permanent outposts on the surfaces of the Moon and Mars could be the first major steps towards the expansion of human civilization into the rest of the solar system. Unaided traction for human walking requires a gravity that is at least 10% of the gravity at the Earth's surface. The Moon, Mars, Mercury, and the Jovian moon, Callisto, are all worlds that have surface gravities higher than 0.1 g. So these are extraterrestrial worlds that will probably be accessible for continuous human occupation before the end of the century. However, whether such low gravity environments would have significant deleterious effects on human health and reproduction is currently unknown. But long before the permanent settlement of extraterrestrial worlds, human outpost on the Moon and Mars, could have beneficial scientific, commercial, and even strategic benefits for those nations and businesses that dare to venture there.

Planets and Moons within the solar system that are potentially suitable for human colonization:

Moon

surface area relative to the Earth: 7.4%

surface gravity relative to the Earth: 0.17g

diameter relative to the Earth: 27.3%

Mars

surface area relative to the Earth: 28.4%
surface gravity relative to the Earth: 0.38g

diameter relative to the Earth: 53.1%

Mercury

surface area relative to the Earth: 14.7%
surface gravity relative to the Earth: 0.38g

diameter relative to the Earth: 38.3%

Callisto

surface area relative to the Earth: 14.3%
surface gravity relative to the Earth: 0.13g

diameter relative to the Earth: 37.8%

Note: Land area comprises 29% of the Earth's surface with 71% covered by water

Regolith shielded habitat designed for the Moon and Mars. Mobile water tanker provides water to the habitat for drinking, washing, growing food, and for the production of air.

Internal view of a regolith shielded habitat with regolith placed within the two meter cavity within the automatically deployed walls surrounding the 8.4 meter in diameter pressurized habitat.

Permanent outpost on the surface of the Moon could immediately exploit
lunar regolith to protect humans from significant exposure to harmful
levels of radiation. Just two meters of lunar regolith dumped within
the walls of a lunar regolith habitat could reduce annual cosmic
radiation exposure below the maximum legal limit for radiation workers
on Earth (5 Rem per year) during the solar minimum while also
protecting astronauts from radiation exposure from major solar events.
Protection from micrometeorites and extreme temperature fluctuations
would be an added benefit of insulating a lunar habitat with regolith.

A single lunar habitat derived from the technology used to make the light weight 8.4 meter in diameter hydrogen fuel tanks for the SLS could provide two levels of floor space approximately 111 square meters in area. That would be more floor space than the average home in Germany, Japan, Sweden, Italy, Spain, Russia, and in the UK. The deployment of such habitats for the private commercial community could also be used as lunar hotels for space tourist or to house workers for private companies involved in the export of lunar water or regolith for government and private entities.

Creating solid pavement for the deployment of habitats and other lunar outpost components upon dust free surfaces could be created by using mobile robots to pave and sinter lunar regolith. This could eliminate tracking in deleterious lunar dust into pressurized habitats when astronauts are working in the paved lunar outpost area.

Mobile water tanker for storing and transporting water and a mobile water extracting robot that uses microwaves to extract water from regolith from the shadowed areas of the lunar poles.

In the lunar polar regions, roving microwave water extraction robots could mine ice particles from the permanently shadowed areas for the production of water. Water, of course, can be used for drinking, washing, food preparation, and for growing food. Water can also be electrolyzed for the production of oxygen for air and for the production of hydrogen and oxygen for rocket fuel needed to return to Earth.

Human biowaste could be converted into methanol through pyrolysis. Methanol and oxygen can be used with fuel cells to produce electricity for back up energy during periods of lunar darkness. The water produced from the combustion of methanol and oxygen can be
recycled. The CO2 produced from the manufacture of methanol and from the combustion of methanol in fuel cells can be used to enhance the growth of indoor lunar
crops. Small portable methanol fuel cells could also be used to provide power for pressure suits during lunar excursions.

Nitrogenous biowaste, such as urine, could be used as fertilizer for lunar crops.

However, there is some evidence that substantial quantities of carbon and nitrogenous material may also be a significant component of the permanently shadowed areas at the lunar poles. Astronauts stationed at lunar outpost at the lunar poles could used to explore and to quantify the amount of volatiles located within the shadowed regions.

Buried nuclear power plant on the lunar surface (Credit: NASA)

While solar panels attached to the habitats would provide the initial power for a lunar habitat, small nuclear reactors buried beneath the lunar regolith only a few hundred meters away could provide substantial amounts of electricity for the lunar facility, 24 hours a day.

Outposts originally designed for the lunar surface could also be utilized on the surfaces of Mars, Mercury, and Callisto and
even on the meager surfaces of large asteroids and on the moons of Mars.

Three regolith shielded habitat modules on a sintered Martian surface area. Each habitat module is connected to each other by two inflatable pressurized walkways.

Permanent outpost on the Moon and Mars and on other worlds, would allow the continuous exploration of those surfaces by both humans and robots. Unmanned solar or nuclear powered rovers on the lunar surface, operated by humans on Earth, could visit and collect samples from practically every area on the surface of the Moon. The collected rocks and soil could then be returned to the lunar outpost for immediate study or for eventual export back to Earth.

On Mars, both robotic rovers and hydrogen blimps could be utilized to continuously explore the Martian surface. Such robots could be operated in real time by the astronauts on the Martian surface or in orbit around Mars at a space station. Again, the collected samples by the remote controlled robots could be returned to the Martian outpost for immediate study or for eventual export back to Earth.

A permanent US government presences on the surface of the Moon and Mars will also enhance the ability of private American companies to protect their assets from potentially hostile foreign entities that will probably also be on these new worlds by mid century.

Tuesday, May 13, 2014

In 2031, a reusable OTV-400 places a boom contracted artificial gravity habitat (AGH) and two Extraterrestrial Landing Vehicles (ETLV-2) into high Martian orbit for a 60 day mission of human exploration of the two Martian moons, Deimos and Phobos, before refueling at a pre-deployed orbiting fuel depot for the return trip to cis-lunar space.

The relatively weightless conditions of orbital and interplanetary space are inherently deleterious to human health.Humans and other terrestrial animals have evolved their physical and physiological attributes under our planet's heavy gravitational environment.

On the surface of the Earth, the human heart has to counter the downward pull of gravity in order to pump adequate amounts of blood to the head and torso when people are standing erect, while blood flowing to the lower limbs is aided by the pull of gravity. But under the microgravity conditions of space, human blood disproportionately flows to the head and torso while blood flow to the lower limbs is reduced. This makes the human face look puffy while their legs become thinner.

Such blood flow redistribution can sometimes cause nausea and headaches when astronauts first arrive in orbit but usually disappears after a few days in space. But other minor but annoying problems can be experienced under weightless conditions, including:

1. Weight loss: the less strenuous conditions diminish appetite, resulting
in weigh loss which could become excessive if astronauts don't exercise
and eat regularly.

2. A degraded sense of smell and taste: your favorite foods could taste a little different under microgravity

3. Clumping of tears and perspiration: there's no gravity to force trickles of water to run off the human body

4. Facial and speech distortions: the face becomes puffy and the voice tone and pitch becomes more nasal

5. Increased flatulence: since digestive gasses no longer rise towards the mouth, their is an increase in gas being expelled through the posterior orifice

The problems listed above could be viewed as only a minor inconvenience on short missions into space. But during long interplanetary journeys lasting months or years, such problems could be annoying enough to enhance stress and increase tension aboard ship.

But there are other, more serious health problems that the human body may be subject to during months or years in a microgravity environment:

1. Astronauts can lose between 1 to 1.5% of their bone mass in a single month

2. Without regular exercise, astronauts can lose up to 20% of their muscle mass in just 5 to 11 days.

3. A microgravity environment can reduce cardiovascular fitness

4. Vision problems of varying degrees of severity can occur especially in older men

5. Blood flow redistribution in a microgravity environment can effect medicines ingested or injected into the human body.

6. Fluid loss and bone demineralization in a microgravity environment can increase the blood's calcium concentration, increasing the risk of an astronaut developing kidney stones.

7. The infected spray from the cough or the sneeze an ill person on board floats in the air instead of falling to the floor, enhancing the spread of infection aboard ship-- especially in a confined environment.

Returning to Earth after a few months aboard the ISS, the blood pressure of some astronauts drops abnormally low when they move from a lying position to a sitting or standing position. Some astronauts even have problems standing up, walking, and turning and stabilizing their gaze.

Since conjunction class missions to Mars may take more than seven months, there could be some question as to whether or not astronauts would have the physical ability to perform a mission to the Martian surface. Astronauts would have to endure weightless for several more months during their return trip from Mars to Earth.

One possible solution to the deleterious effects of weightlessness would be temporary periods of high simulated gravity (hypergravity). On Earth, sustained
bed rest on a flat surface that is tilted a few degrees backwards can simulate the deleterious effects of a microgravity environment, causing more blood to rush
towards the head and less blood to flow into the hind limbs. But if such beds are attached to a short radius centrifuge, high levels of G forces can be experienced at the human foot level.

Short radius hypergravity centrifuge could help to mitigate the deleterious effects of a microgravity environment on the human body (Credit NASA).

Hypergravity studies have shown that protein synthesis in the leg muscles can be sustained if 2.5 G is experienced for just one hour a day at the foot level during a 21 day period. This suggest that daily exposure to a brief period of hypergravity in space may be an effective counter measure, mitigating the loss of muscle mass in a microgravity environment.

Production of the 8.4 meter section of the SLS hydrogen fuel tank. Such components could be used for reusable common bulkhead interplanetary vehicles or for pressurized human space habitats (Credit Boeing Aerospace).

Short radius hypergravity centrifuges require a radius of more than 3 meters to accommodate the human body. So space habitats utilizing such centrifuges would have to have unobstructed internal diameters of more than six meters. Habitats derived from the SLS hydrogen fuel tanks could have an internal diameter as large as 8.4 meters. Even surrounded by 50 centimeters of water for radiation mass shielding would still give a habitat 7.4 meters in diameter of space to accommodate such machines.

SLS hydrogen fuel tank derived Skylab II concept (Credit Griffin).

So an SLS hydrogen fuel tank derived habitat such as the Skylab II concept could easily accommodate a short radius hypergravity centrifuge to keep astronauts and possibly even space tourist healthier while in orbit or on an interplanetary journy.

However, it has yet to be determined whether
short centrifuge hypergravity machines can also alleviate some of the
other serious physical and physiological problems associated with a
weightless. And temporary hypergravity would have no effect on the enhanced
spread of infectious diseases and some of the minor but annoying problems associated
with weightlessness.

To eliminate all of the problems associated with a microgravity environment during long periods of space travel, a continuous artificial gravity environment would be required.

In order to mitigate the physiological effects of Coriolis, a habitat capable of producing at least 0.5g of simulated gravity (higher than the gravity on the Moon and Mars) would require a rotation of approximately 2rpm (rotations per minute) and a radius of at least 112 meters. That would require a rotating habitat approximately 224 meters in diameter if twin counterbalancing pressurized habitats were utilized.

Artificial Gravity Habitat (AGH) located at EML4 or EML5 and radiation shielded with iron enriched lunar regolith to reduce annual radiation levels for inhabitants to below those allowed for radiation workers on Earth.

A rotating habitat derived from SLS hydrogen fuel tank technology under this scenario would require two SLS launches to deploy and assemble the structure at one of the Earth-Moon Lagrange points. A core module would contain a pressurized docking section, solar panels, plus extendable cables, boom, and twin cable elevators on each side. Two external air locks derived from the SLS upper stage oxygen tank technology would also be deployed during this launch.

A second SLS launch to the Lagrange points would deploy two twin pressurized habitat modules that would connect to each side of the previously launched the core module. The total structural mass of the AGH (Artificial Gravity Habitat) is assumed to be less than 60 tonnes before the habitat modules are internally mass shielded by water for interplanetary journeys or with iron enriched regolith for permanent space stations.

Each AGH pressurized habitat module would provide shielded living area equivalent to a small two story homes, providing a spaciously comfortable environment for scientist and astronauts who may have to live in the confined simulated gravity habitats for several months or even a few years.

AGH habitat module that can be internally shielded with 50 cm of water for interplanetary journeys or 50 cm of iron enriched regolith for permanent space stations.

A crewed or automated OTV-2 vehicle (derived from the ETLV-2) would be utilized to help assemble the AGH structure: docking the external airlocks to the sides of the core module and docking the habitat modules to both ends of the core module.

OTV-2 orbital transfer vehicle positioning the second habitat module to be docked with the core module of an Artificial Gravity Habitat (AGH) at EML4 or EML5.

The expandable boom would be rigid enough to allow thruster pods located at the ends of the habitat modules to increase or decrease its rate of the AGH rotation while the boom and internal cables are fully extended. Steel cables within the external boom would connect the AGH habitat modules to the core module. The cables would pull in the habitat modules before rocket burn maneuvers were conducted, expanding them again once the delta-v maneuvers are over. The hollow boom would also enhance the visibility of the AGH when crewed vehicles are approaching the central axis to dock.

For interplanetary journeys, the twin habitat modules would be shielded with water 50 cm thick. This would reduce astronaut's exposure to cosmic radiation to approximately 20 Rem per year during the solar minimum while also protecting astronauts from major solar events. Internally water shielding two levels of inhabited area within a pressurized habitat would add approximately 118 tonnes of weight to each habitat. Twin habitats, therefore, would add an additional 236 tonnes of mass to an interplanetary vehicle. So an AGH shielded for interplanetary travel would weigh nearly 300 tonnes, not including the additional mass for food, water, and air for the crew. Over the course of 1000 days, a crew of ten would add at least 50 tonnes of additional mass to the vessel unless their was significant recycling of both air and water.

At 5.2 km/s to 7 km/s, the delta-v requirements for transporting such a massive vehicle from
LEO to Mars orbit could be prohibitive. However, if the interplanetary
vehicle was fueled and launched from the Earth-Moon Lagrange points to
high Mars orbit, the delta-v requirements could be less than 2 km/s.

Delta- V Budget from Cis-Lunar Space to Mars Orbit

EML1 or EML2 to Mars Capture Orbit -- 1.64 km/s

EML4 or EML5 to Mars Capture Orbit - 1.93 km/s

EML1 or EML2 to Low Mars Orbit ------ 3.04 km/s

EML4 or EML5 to Low Mars Orbit ----- 3.33 km/s

LEO to Mars Capture Orbit ---------------- 5.2 km/s

LEO to Low Mars Orbit -------------------- 7 km/s

Liquid hydrogen and oxygen fueled cryogenic propulsion stages have
been proposed by SpaceWorks with a fuel capacity of over 450 tonnes but
with n inert weight of less than 30 tonnes. The ULA has proposed a
cluster of six ACES boosters with a LOX/LH2 fuel capacity of approximately 700
tonnes.

Under this scenario, a common bulkhead LOX/LH2 fuel tank derived from the SLS hydrogen tank technology is utilized for a reusable interplanetary booster in order to minimize development cost. The OTV-400 would be capable of storing up to 400 tonnes of fuel for crewed interplanetary journeys to Mars, Venus, and the near
Earth asteroids. The standard 400 tonne fuel tank is also utilized for
large fuel depots under this scenario in order to minimize
cost. Integrated Vehicle Fluid (IVF) technology would utilize ullage
gases for tank pressurization and attitude control. Cryofuel boil-off would be eliminated during interplanetary journeys by using solar powered
cryocoolers.

A single SLS launch would be required to deploy the OTV-400 to
LEO with enough fuel to travel to an Earth-Moon Lagrange point for
refueling. Less than 350 tonnes of fuel would probably be required for
a crewed interplanetary journey to high Mars orbit, including two fully
fueled Extraterrestrial Landing
Vehicles.

Launching human interplanetary missions from the Earth-Moon Lagrange
points to high Mars orbit rather than from LEO has several advantages.

1.
To travel from an Earth-Moon Lagrange point to high Mars orbit requires
less than 2 km/s of delta-v. But traveling from LEO to high Mars orbit
would require more than 5 km/s of delta-v.

2. The
delta-v requirement to transport water for shielding and fuel to an
Earth-Moon Lagrange point is less than 2.6 km/s. The delta-v requirement
to transport water to LEO is more than 9 km/s

3. The
vehicles required to transport water to from the Moon to the Earth-Moon
Lagrange points could be used for at least ten round trips before their CECE
engines would have to be replaced or a new vehicle would be required.
The vehicles required to transport water from Earth to LEO, however, would be
expendable and could only be used once.

Reusable OTV-400 attached to a contracted AGH during propulsive delta-v maneuvers and a reusable OTV-400 attached to an expanded rotating AGH after the completion of a propulsive delta-v maneuver.

The interplanetary vehicles return trip from Mars to cis-lunar space
would require the OTV-400 to refuel at a previously deployed depot in high Mars
orbit. Fuel depots in
orbit around Mars would initially use water exported from the lunar
surface to manufacture fuel. But eventually, lunar derived water
producing and exporting machines and vehicles would be placed on the
surfaces of Deimos and Phobos for water production and export to the
Mars orbiting fuel manufacturing depots.

An OTV-400 derived fuel depot (WFD-400) capable of producing cryogenic hydrogen and oxygen from stored water. The WFD-400 would be capable of transporting itself anywhere within cis-lunar space or into orbit around Mars or Venus.

For permanent space stations at the Earth-Moon Lagrange points or in orbit around Mars, the twin habitat modules would require a radiation shield of iron enriched regolith about 50 cm thick to reduce cosmic radiation exposure to less than 5 Rem annually (maximum allowed for radiation workers on Earth) during the solar minimum. That would require nearly 1865 tonnes of mass shielding (932 tonnes of iron enriched regolith for each habitat module). This would require one or two SLS launches of twin reusable regolith shuttles to the lunar surface-- depending on whether or not the CECE engines on the regolith shuttles are replaced after ten round trips.

Delta-V requirements to transport water for fuel, air, drinking, and mass shielding to LEO or to the Earth-Moon Lagrange Points

Lunar surface to EML1 --------------------- 2.52 km/s

Lunar surface to EML2---------------------- 2.53 km/s

Lunar surface to EML4 or EML5 ---------- 2.58 km/s

Lunar surface to LEO (with aerobraking) - 2.74 km/s

Earth's surface to LEO ----------------------- 9.3 km/s

Earth's surface to EML2 ------------------- 12.73 km/s

Earth's surface to EML1 ------------------- 13.07 km/s

Earth's surface to EML4 or EML5 ------- 13.27 km/s

Reusable lunar tankers capable of delivering more than 50 tonnes of water or regolith to the Earth-Moon Lagrange points. Their CECE engines should be capable of at least ten round trips from the lunar surface to the Lagrange points before the engines, or the entire vehicle, needs to be replaced. So after ten round trips, each vehicle would be capable of delivering more than 500 tonnes of fuel or regoltih to the Earth-Moon Lagrange points.

Transporting an iron enriched regolith shielded space station to high
Mars orbit would obviously require a much larger vehicle than the
OTV-400. A light sail with a surface area of at least 100 square
kilometers should be able to transport a few thousand tonnes to Mars
within a years time. But if light sail technology is still not
available, vehicles capable of transporting a few thousand tonnes to
Mars orbit could easily be assembled by clustering four or more OTV-400
tanks around a core tank. A cluster of five OTV-400 vehicles would
create an OTV-2000 interplanetary booster. A cluster of seven OTV-400
boosters would create an OTV-2800 interplanetary booster. Large
clustered LOX/LH2 fuel tanks have also been proposed by the ULA for
their human interplanetary vehicle concepts.

The fuel requirements for such large interplanetary vehicles under this scenario would require one or two SLS launches of reusable water shuttles to the lunar surface. The lunar tankers would then transport water manufactured on the Moon to fuel manufacturing depots at L4 or L5. Again, such lunar tankers should be capable of at least ten round trips before their CECE engines would need to be replaced.

OTV-2000 is comprised of a cluster of five OTV-400 boosters.

The OTV-400 would give NASA and possibly private space companies the delta-v capability to conduct human missions from the Earth-Moon Lagrange points to the orbits of Mars and Venus, and to the NEO asteroids, and to Sun-Earth L4 and L5 as long as fuel depots for the return trip to cis-lunar space are pre-deployed at those destinations.

OTV-2000 and OTV-2800 class of interplanetary boosters could
enable human journeys from the Earth-Moon Lagrange points to the asteroid belt to places like Ceres and Vesta, again with WFD-OTV- 2000
or 2800 fuel depots pre-deployed in orbit around such large asteroids.

"The knowledge that we have now is but a fraction of the knowledge we must get, whether for peaceful use or for national defense. We must depend on intensive research to acquire the further knowledge we need ... These are truths that every scientist knows. They are truths that the American people need to understand." (Harry S. Truman 1948).